Before I get into the details of what's about to happen, I want to
make sure we understand the territory. We're about to discuss things
that range in size by a factor of a billion to one, so it's useful to
go over the distance scale so we don't confuse millions and billions
the way the politicians do.

Let's start with the measure of all things, a human being. Humans
are on the order of metres in size, actually closer to two metres, but
we can ignore ones and twos when talking about factors of 1000, as
we're about to do.

Most of the history of technology has been built to this scale, and
tended to look something like this.

If an object has to be assembled by people, in many cases powered by
people, and operated by people, it doesn't make any sense to make it
smaller than people can reasonably use, notwithstanding the design
of modern car stereos.

The size of mechanical parts is governed by the
materials that compose them and the scale of the machines used to
fabricate them. Both imposed severe limitations on miniaturisation
throughout most of history, limitations that were surmounted only with
great difficulty and expense when absolutely necessary, as in the
design of watches.

Wherever technology leads us, effective design at this scale will
remain important as long as humans use the products.
This is the domain of user interface and ergonomics.